autocorrect

Why is it that almost every single time I change the keyboard from alpha to numbers, it corrects the last word I spelled? Literally 90% of the time. It makes absolutely no sense to me, and is driving me crazy.
Can you please fix this? It's something that started happening in 1.6.3906, the version I now have.

For example, type something where you want to end with a question mark. As soon as you change from letters to numbers, the last word is auto-corrected - typically to something that makes zero sense.